Decompression device for valve-controlled combustion engine



United States Patent [1113,540,424

[72] Inventors Mann-ed Dietel [56] References Cited schweinm'i' ce'mnyi UNITED STATES PATENTS Kmhem Niederwerm Germany 1,805,578 5/1931 Gardner et al 123/182 253 0 April 12 1968 3,319,619 5/1967 Never 123/182 45 Patented N 7 3,342,169 9/1967 Farny et al 123/182 [73] Assignee Motorenfabrik Hatz GmbH F REIGN PATENTS Rushstorf, Germany 451,428 8/1936 Great Britain 123/182 [32] Prior" z grg ga Germany Primary Exam iner- M ark M. Newman [33 1 y g Attorney-Larson, Taylor and Hinds s 1 1 E 31,998 1 ABSTRACT: A decompression device for valve-controlled internal combustion engines. A decompression control cam is nonrotatably mounted on a spindle coaxial with the valve rocker arm spindle and is operatively connected to the rocker [54] arm so that rotation of the cam from a reference position 6 Claims finnwi m s prevents closing of the valve. The cam may be operated to g maintain decompression indefinitely, or it may be set to act, US. Cl 123/182 through means operatively connecting the two spindles to ter- F01] 13/08 minate decompression after a predetermined number of rota- Field of Search 1. 123/182 tions of the engine crankshaft.

Patented Nov. 17, 197% 3,54%424 Sheet 1 n2 Patented Nov. 17, 1970 Sheet 012 l DECOMPRESSION DEVICE-FOR VALVE-CONTROLLED 1 COMBUSTION ENGINE BACKGROUND OF THE INVENTION l. Field of the Invention This invention 'relates to internal combustion'engines; and in particular it relates to a decompressiondevice for valvecontrolled internal combustion engines;

2. Description of the Prior Art Decompression devices for valve-controlled combustion engines, particularly injection combustion engines, are known. They are used to assist the starting of small engines, particularly diesel combustion engines, which often are started manually by means of a handcrank. To this end a valve is held open during the starting operation with the help of the aforesaid decompression device, whereby that part of the resistance to the turning of the handcrank attributable to the compression in the engine is greatly reduced. A further easing of the starting procedure is afforded. by automatically eliminating the decompression after a preselected number of rotations of the crankshaft. Known decompression devices additionally provide both (a) prolonged lifting of thevalve until the decompression means is manually removed and (b) means for automatically eliminating the valve decompression means. The prolonged valve lift is of importance at extremelylow temperatures. It enables the film of lubricant on the cylinder walls to be warmed before the actual starting procedure is commenced, and this in turn facilitates starting.

In the knownarrangements the decompression cam and the driving element, cooperate with an actuating member ar- SUMMARY OF THE INVENTION A purpose of the present invention therefore is to provide an improved decompression device which is distinguished from the known constructions by a simple structure and a notably greater-functional reliability.

According to the present invention, the decompression cam and the driving element,.referred to hereafter as a driving disc,

are nonrotatably arranged on a decompression spindle which is disposed coaxially with the axis of the valve rocker, and which preferably has one end projectingout of the housing of the valve gear and coupled to a hand adjusting lever.

With this structure it is possible toautomatically terminate decompression (permit the valvevto close) in response to the accurately definable rotaryimovement of the valve rocker.

According to one feature of the invention, the decompression cam preferably comprises a disc provided with two lateral flanges, these flanges providing a very simplemethod of coaxially guiding anabutment piece which bears'against the surface of the cam and is coupled to the rocker.

According'to a further feature of'the :invention the driving disc, which is spacially' separated from the decompression cam, is arranged on the same spindle as the latter, is axially displaceable and nonrotatably arranged on this spindle, and is in the form of a bush which is provided over a part of its periphery, at the face thereof confronting an actuating member, with'a-saw tooth profile. This arrangement has the attributes of accurate guidance of the driving bush on the spindle, and of small frictional effects on the driving bush. Because of the physical separation of the decompression cam and the driving disc or bush, .a correct disengagement of these elements if ensured when this becomes necessary.

An advantage of the present invention is its simplicity. This simplification of the structure is achieved in that the actuating member is preferably formed as a disc which is mounted on the rocker spindle and is nonpositively coupled to the rocker.

According to yet another feature of the invention, the disc used as the actuating element has two lugs which are bent over in the axial direction, one of these lugs being in operative engagement with the saw tooth profile of the driving disc, and the other lug engaging nonpositively in a recess in the rocker. This construction permits a reduction in the number of parts which are required in building a decompression device of the present kind.

According to still a further feature of the invention a helical compression spring may be placed between the decompression cam and the driving disc, which preferably is in the form of a bush. The resilient element which is required for the indexing movement thereby consists of a compression spring and offers the advantage that the pressure between the driving disc'and the actuating member can be accurately controlled.

Thus, it is a purpose of the present invention to provide a new and improved valve decompression device for an internal combustion engine.

It is another object of this invention to provide a valve decompression device which may be operated either manually or automatically and which is bothsimple and more accurate than decompression devices of the same general type known heretofore.

It is still another object of this invention to provide a valve decompression device for use with an internal combustion en gine wherein a decompression cam and a driving disc are mounted on a spindle which is coaxial with the axis of the valve locker arm. I

Other objects and the attendant advantages of the present invention will become apparent from the detailed description to follow together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Although there follows a detailed description and accompanying drawings of a preferred embodiment of the invention, it is to be understood that the invention is capable of numerous modifications and variations apparent to those skilled in the art.

In the drawings:

FIG. 1 is a section through the decompression device taken through the axis of the valve;

FIG. 2 is a sectional view taken on line II-II of FIG. 1;

FIG. 3 is a plan view of the device illustrated in FIG. 1;

FIG. 4 is a view inthe direction of arrow A of FIG. 3;

FIG. 5 illustrates the end face of the driving disc viewed from the right as shown in FIG. 2 and showing the partially saw-toothed profile of the disc; and

FIG. 6 is a partial elevational view taken in the direction of the arrow A in FIG. 3.

DETAILED-DESCRIPTION OF THE PREFERRED EMBODIMENT Referringnow to the drawings, an exhaust valve member 2 in the valve housing 1 of an injection type internal combustion engine of known construction is pressed upwards againsta valve seat 4 by a closure-spring 3. A plunger 5, movable up and down by an operating mechanism (not shown), engages the double-armed rocker 6 which is adapted to move valve member 2 downwardly in the opening direction. The rocker 6 is mounted in the valvehousing 1 on a rocker spindle 7. When plunger-5 moves upwards the valve is opened, and when it moves downwards the valve is closed under the action of spring 3. I

The decompression device comprises a decompression cam 8 which acts on rocker 6=and can be turned by hand or by an automatic mechanism so as to cut off the decompression effect, and a driving discv 10 connected to the decompression cam and operatively coupled through actuating member 13 with the rocker 6.

The decompression cam is constituted by a plate having two radial side flanges 16 and is nonrotatably connected to a decompression spindle 9 extending coaxially with the rocker spindle 7. Mounted on the decompression spindle 9, adjacent the decompression cam 8, and held on this spindle. so as also to be nonrotatable but axially displaceable on the same, is the driving disc 10 which is in the form ofa bush.

The driving disc 10 has at the end face thereof directed towards an actuating member 13, an area 18 with a sawtooth profile, and a further area 19 which is nontoothed, [.e. is flat. The actuating member 13 is in the form of a plate provided on the axis of spindle 7 and nonpositively connected on the rocker 6. The member 13 has two lugs 14 and 15 which are bent over so as to extend in the axial direction, one such lug 14 being in operative engagement with end face of driving disc 10 having the sawtooth profile 18 of the driving disc 10 as best shown in FIG. 6, and the other lug 15 engaging nonpositively in a corresponding recess in the rocker 6. Referring to FIG. 5, wherein the'rest position of lug 14 is superimposed in dotted lines, the lug 14 rides through the range Y over that portion of the end face on the right and just below the horizontal plane through the axis of the end face.

A helical compression spring 11 is arranged between the decompression cam 8, which is nonrotatably fastened to the decompression spindle 9 by a clamping pin 25, and the driving disc 10 which is axially displaceable on the same spindle 9. The disc 10, thereby biased by the helical spring 11, bears against the end face of the rocker spindle 7. To provide for an axially displaceable, but nonrotatable arrangement of the driving element 10, the latter is provided with a longitudinal slot 24 into which passes a cylindrical pin 23 secured to the decompression spindle 9.

The decompression cam 8 is formed by a plate ofcylindrical contour which is flattened over a part of its periphery by a milled portion 31.

An abutment member 17 is axially guided on the surface of the decompression cam 8 between the radial side flanges 16. This member 17 is pivotally secured in the valve housing 1 by means of a split pin 21 and with an interposed compression spring 22. The spring 22 serves to provide a nonpositive coupling between member 17 and the decompression cam 8. This abutment member 17 is a main link between cam 8 and rocker 6. Unhampered movement of the rocker 6, and thus closing of the valve 2, is possible only when the abutment member 17 bears against the flat 31 of the decompression cam. Thus the member 17, together with the setscrew on one end of the rocker 6, provides an adjustable abutment.

Turning of the decompression cam 8, and hence operation of the decompression device, is effected through the hand adjusting lever 12 arranged externally of the valve housing 1 on the decompression spindle 9. This lever 12 is nonrotatably coupled to spindle 9 by means of a cylindrical pin 26. The operative position ofthe hand adjusting lever 12, once set, can be secured by a ball catch 29 which engages in a detent 30 in the decompression spindle 9 under the force ofa compression spring 28 and a threaded pin 27.

The illustrated preferred embodiment of the invention operates as follows.

When the internal combustion engine is running the decompression device is out of action because the abutment member 17 bears on the milled out or flat part 31 ofthe decompression cam 8. With the decompression cam set in this way, the setscrew 20 of the rocker 6 does not strike the abutment piece 17 and this means that the exhaust valve 2 can be closed. Moreover the automatic decompression terminating means is inoperative because the lug 14 of the actuating member 13 moves over the flat, nontoothed area 19 of the driving disc 10. The hand adjusting lever 12 occupies the position B illustrated in solid lines in FIG. 4 and is held in this position by the ball catch 29.

When protracted lifting of the exhaust valve 2 is required, the hand adjusting lever 12 is moved into the position C illustrated in dotted lines in FIG. 4, and when automatic decompression termination is required, the lever 12 is turned to position D as also shown in dotted lines in FIG. 4.v In both instances the abutment member 17 is moved away from the flat 31 of the decompression cam to the raised cylindrical part of the surface of the latter, as a result of which the exhaust valve 2 is opened a predetermined amount through the agency of the setscrew 20 and the rocker 6. The hand adjusting lever is held in positions C or D by ball catch 29 as it was when in position B.

The number of turns of the starting crank before the decom pression is automatically terminated can be selected by means of the hand adjusting lever 12. In position D lever 12 is set for the maximum number of turns since tooth 18a is now located adjacent lug l4 and the disc 10 will now turn clockwise (FIG. 5) until the last tooth 18b is turned by lug 14, at which time the rest position B (as shown in FIGS. 5 and 6) will be reached. If the hand setting lever 12 is turned in the counterclockwise direction (FIG. 4) from position D, this means a correspondingly smaller number of turns of the starting crank before the decompression terminates. The user thus has a choice of the period for which decompression is to be applied.

With the hand setting lever 12 in position D, the abutment member 17 is lifted into the position illustrated in dotted lines in FIG. 1 through the agency of the decompression cam 8, with the result that the range of pivoting of the rocker 6 for decompression is restricted. At the same time the first tooth 18a of the sawtoothing provided on the end face of the driving element is brought into engagement with the tooth-formed lug 14 of the actuating member 13 and nonpositively coupled thereto by the helical compression spring 11. If the rocker arm 6 is now moved counterclockwise (FIG. 1), then valve 2 moves downward and the member 13 is turned by the same angular magnitude as rocker arm 6 in the direction of the decompression, that is to say in a counterclockwise direction (FIG. 1). This angular magnitude Y corresponds to the angular distance between two teeth 18. Since in this position the point of projection 14 would be behind the axis-parallel plane of a tooth 18, part 10 is carried along with projection 14, in the case of this revolution of parts 6 and 14, through the range Y from the solid line position oflug 14 in FIG. 6, to the dotted line position of lug 14 in FIG. 6. The friction in the notch 29, 30 will be overcome through the positive engagement of parts 14 and 18, so that part 10 and shaft 9 (via 23) together with the decompression cam 8 (via 25) are turned by an angular value corresponding to the distance Y between the teeth. If subsequently the rocker arm 6 is then moved clockwise (FIG. 1) and valve 2 moves up, then the lug 14 is moved back by the same said angular value corresponding to the distance between two teeth 18. Now the projection 14 glides along the inclined plane of tooth l8, and friction between elements 29 and 30 will be greater than the friction between parts 14 and 18, so that elements 9 and 10 will not rotate. To permit lug 14 to pass over the tip of tooth 18 and drop behind the next tooth 18, disc 10 will shift to the left in relation to the standing shaft 9 (FIG. 2) by the small amount X (FIG. 6). This cycle is repeated until the lug 14 of actuating member 13, acting as a tooth, passes behind the last tooth 18b of the saw-toothed profile 18 at which time the milled portion 31 again passes beneath the abutment piece 17 and decompression is terminated. The hand adjusting lever 12 has then automatically resumed position B.

Finally it is pointed out that the pattern of movements of the automatic decompression termination device, described above, is ensured by the sawtooth form of the toothing on the driving element 10 and by the device which arrests the decompression spindle 9 and acts as a brake, namely comprising the parts 11, 12 and 14.

Although a preferred embodiment of the invention has been described in considerable detail it should be apparent that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit or scope of the invention.

We claim:

1.- A decompression device for a valve-controlled combustion engine including a valve, a rocker mounted for rotating movement to open the valve and to permit closing of the valve, a decompression cam nonrotatably mounted on a spindie, said spindle mounted for rotation about an axis coaxial with the axis of rotation of the rocker, mechanical means acting in response to the position of the decompression cam for either permitting or preventing the necessary movement of the rocker arm to permit the valve to close, and a decompression termination means including a driving disc nonrotatably mounted on the spindle, including an actuating means comprising a actuating member for operatively engaging the rocker and said driving disc to control rotation of the disc in response to movement of the rocker and thereby control rotation of the spindle and decompression cam, said driving disc being mounted on the spindle for axial displacement along said spindle and being provided at one end with a sawtooth profile extending over a part of its circumference, said actuating member comprising at least one lug bent over in the axial direction and engaging in said sawtooth profile, and a spring mounted to axially displace said driving disc and to urge the sawtooth profile into engagement with said lug, said device being such that the actuating member turns the driving disc with it in response to the movement of the rocker in one direction and causes an axial displacement of said driving disc without turning the driving disc in response to the movement of the rocker in the reverse direction.

2. A decompression device according to claim 1 wherein said spring is formed as a helical compression spring encircling said spindle between the decompression cam and the driving disc.

3. The decompression device of claim 1 including a handle attached to the spindle for manually adjusting the position of the spindle.

4. A decompression device according to claim 1 wherein the decompression cam is constituted by a disc which is provided with two lateral flanges, and said mechanical means is an abutment piece connected to the rocker and applied against the peripheral surface of the cam between these flanges.

5, A decompression device according to claim 1 wherein the said actuating member is constituted by a plate which is mounted on the axis of the rocker and is positively coupled to this rocker.

6. A decompression device according to claim 5 wherein the plate has two lugs bent over in the axial direction, one of these lugs being the said lug operatively engaged with the said tooth profile of the driving disc, and the other lug operatively engaging in a recess in the rocker. 

